The steady state and transient characteristics of a molten salt natural circulation loop (NCL) are obtained by 3D CFD simulations. The working fluid is a mixture of NaN0₃ and KN0₃ in 60:40 ratio. Simulation is performed using PHOENICS CFD software. The computational domain is discretized by a body fitted grid generated using in-built mesh generator. The CFD model includes primary side. Primary side fluid is subjected to heat addition in heater section, heat loss to ambient (in piping connecting heater and cooler) and to secondary side (in cooler section). Reynolds Averaged Navier Stokes equations are solved along with the standard k-ε turbulence model. Valid@- tion of the model is done by comparing the computed steady state Reynolds number with that predicted by various correla- tions proposed previously. Transient simulations were carried out to study the flow  initiations transients for different heater powers and different configurations. Similarly the 'power raising" transient  is computed and compared with in-house experimental data. It is found that,  sing detailed information obtained from 3D transient CFD simulations, it is possible to understand the  physics of oscillatory flow patterns obtained in the loop under certain conditions.